In recent years, various kinds of notebook-type or laptop-type portable personal computers have been developed. Most of such personal computers are configured to be battery-powerable. The chargeable capacity of a battery decreases each time the battery is charged. As the number of times of charging of the battery increases, the chargeable capacity of the battery becomes smaller.
In usual cases, “one-time charging” is counted when the battery capacity has varied from a certain lower limit value to an upper limit value at a time by charging. When charging is performed such that the battery capacity has varied within the range between the lower limit value and the upper limit value, “one-time charging” is not counted. Thus, the count value of the number of times of charging is smaller than the value corresponding to the actual charging capacity. Consequently, such a situation would occur that even if the count value of the number of times of charging is less than a certain reference value, the actual chargeable capacity of the battery has considerably decreased.
Jpn. Pat. Appln. KOKAI Publication No. H10-295046 discloses an apparatus of detecting the degradation of a rechargeable battery. This apparatus detects degradation of the rechargeable battery by making use of such characteristics that the charge current tends to increase when the rechargeable battery has degraded. Specifically, this apparatus detects degradation of the rechargeable battery when the charge current of the rechargeable battery is above a threshold value for a predetermined time or more.
However, the charging current that is supplied to the battery may vary due to factors other than degradation of the battery. For example, in an information processing apparatus such as a computer, the charging current that is supplied to the battery may possibly vary due to the load of the information processing apparatus. For example, when the load of the information processing apparatus is large, the charging current that is supplied to the battery from an external power supply may possibly decrease. Thus, in the apparatus of KOKAI No. H10-295046, it is difficult to correctly detect the presence/absence of deterioration of the battery.
Therefore, it is necessary to realize a novel function for correctly detecting the degradation of the battery.